An inhaler is a device used for delivering a medication into the body of a patient or user of the device via the user's lungs. Inhalers are frequently used in the treatment of asthma, Chronic Obstructive Pulmonary Disease (COPD), and other respiratory diseases. For example, a medication such as Znamivir (Relenza), which is used to treat influenza, is administered via an inhaler.
Although various types of inhalers, such as dry-powder and nebulizer devices, have been employed for administering medications, a metered-dose inhaler (MDI) is the most common type used today. The MDI is designed for delivering a specific amount of aerosolized medication, typically in the form of a short burst, to the lungs of the user. In an MDI, medication is most commonly stored in a canister containing a propellant. The propellant is pressurized to provide a force for generating an aerosol cloud and is also the medium in which the medication is suspended or dissolved.
Generally, in the MDI the canister is inserted into the MDI housing and engaged with a specially provided orifice that is designed to direct the medication into the MDI's mouthpiece. During operation of the MDI, typically the canister itself is pressed by the user to dispense the medication.